Observations of very low amounts of precipitable water vapor (PWV) by means of the Ground‐Based Millimeter wave Spectrometer (GBMS) are discussed. Low amounts of column water vapor (between 0.5 and 4 mm) are typical of high mountain sites and polar regions, especially during winter, and are difficult to measure accurately because of the lack of sensitivity of conventional instruments to such low PWV contents. The technique used involves the measurement of atmospheric opacity in the range between 230 and 280 GHz with a spectral resolution of 4 GHz, followed by the conversion to precipitable water vapor using a linear relationship. We present the intercomparison of this data set with simultaneous PWV observations obtained with Vaisala RS92k radiosondes, a Raman lidar, and an IR Fourier transform spectrometer. These sets of measurements were carried out during the primary field campaign of the Earth Cooling by Water vapor Radiation (ECOWAR) project which took place at Breuil‐Cervinia (45.9°N, 7.6°E, elevation 1990 m) and Plateau Rosa (45.9°N, 7.7°E, elevation 3490 m), Italy, from 3 to 16 March 2007. GBMS PWV measurements show a good agreement with the other three data sets exhibiting a mean difference between observations of ≃9%. The considerable number of data points available for the GBMS versus lidar PWV correlation allows an additional analysis which indicates negligible systematic differences between the two data sets.

Compositional data analysis was applied on mineral element concentrations (i.e., Al, Ti, Si, Ca, Mg, Fe, Sr) content in PM₁₀, PM_2.5 and PM₁ simultaneous measurements at three characteristic environmental sites: kerbside, background and rural site. Different possible sources of mineral trace elements affecting the PM in the considered sites were highlighted. Particularly, results show that compositional data analysis allows for the assessment of chemical/physical differences between mineral element concentrations of PM. These differences can be associated with both different kinds of involved mineral sources and different mechanisms of accumulation/dispersion of PM at the considered sites.

The dependence of Ångstrom's turbidity parameters on the wavelength has been analyzed in the wavelength interval 0.45–0.70 μm. Measurements of aerosol optical thicknesses in this range were obtained by a wide-range grating spectrometer with a resolution of ∼ 2.5 nm. Based on such measurements, two different methods for obtaining turbidity parameters have been validated and intercompared: (a) the ratio method based on processing couples of aerosol optical depths, and (b) a linear best-fitting method based on log-log plot of aerosol optical thicknesses vs. wavelength. We found that Angstr̊m's turbidity relation is quite effective in characterizing atmospheric aerosol in low-medium turbidity cases. However, the usual method of computing the turbidity parameters on the basis of a few measurements (< 10) does not produce adequate results. Accurate estimates can be only obtained using a larger number of data points